Neuromuscular Disorders Quiz

Neuromuscular Diseases

• Neuromuscular diseases include disorders of the motor nerve (anterior horn cell and peripheral nerve) such as Polio, CMT (Charcot-Marie Tooth), and ALS (Amyotrophic Lateral Sclerosis), and disorders at the neuromuscular junction such as Myesthenia Gravis. Muscular Dystrophy and Spinal Muscular Atrophy are also considered disorders of the muscle.

Muscular Dystrophy & Spinal Muscular Atrophy

• Muscular Dystrophy (MD) and Spinal Muscular Atrophy (SMA) are characterized by progressive weakness, muscle atrophy, contracture formation, and progressive disability.
• Some cases result in shortened life spans.
• These conditions often have a genetic origin.
• While not curable, they are treatable.

Muscle Disease Characteristics

• Duchenne muscular dystrophy:

  • Onset: 1-5 years
  • Inheritance: X-linked
  • Course: Rapidly progressive; loss of walking typically by 9-10 years; death in late teens.

• Becker muscular dystrophy:

  • Onset: 5-10 years
  • Inheritance: X-linked
  • Course: Slowly progressive; maintain walking past 16; life span into third decade or beyond.

• Congenital muscular dystrophy:

  • Onset: Birth
  • Inheritance: Recessive
  • Course: Course dependent on specific genetics, variable severity, shortened life span.

• Congenital myotonic dystrophy:

  • Onset: Birth
  • Inheritance: Dominant
  • Course: Typically slow with significant intellectual impairment.

• Childhood-onset facioscapulohumeral muscular dystrophy:

  • Onset: First decade
  • Inheritance: Dominant/Recessive
  • Course: Slowly progressive; loss of walking in later life; variable life expectancy.

• Emery-Dreifuss muscular dystrophy:

  • Onset: Childhood to early teens
  • Inheritance: X-linked
  • Course: Slowly progressive with cardiac abnormality and normal life span.

Muscular Dystrophies

• Duchenne: Onset 1-4 years, x-linked, rapid progression
• Becker: Onset 5-10 years, x-linked, slower progression
• Congenital: Onset Birth, recessive, slow progression, shortened life-span
• Congenital Myotonic: Onset Birth, slow progression with significant intellectual impairment
• Facioscapulohumeral: Onset in 1st decade, slow progression, late loss of ambulation, variable life expectancy

Duchenne Muscular Dystrophy

• Incidence: 1 in 3,600-6,000 live male births
• Dystrophinopathy: mutation in the gene coding for the dystrophin protein
• Progression: Child becomes progressively weaker, morbidity related to respiratory insufficiency and/or heart failure
• Inheritance: X-linked pattern; male offspring inherit from asymptomatic mothers

Duchenne Muscular Dystrophy Pathophysiology

• Absence of dystrophin results in a reduction of dystrophin-associated proteins in the muscle cell membrane.
• This causes a disruption in the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix.

DMD - Pathogenesis

• Lack or absence of dystrophin destabilizes the membrane.
• Calcium influx occurs.
• Activation of a calcium-activated proteinase leads to destruction of the cell.
• Muscle cells are replaced by fatty and connective tissue.

Diagnosis of DMD

• Blood work: Creatine Kinase (CK) levels are significantly elevated (100x) even at birth.
• Genetic testing: by blood work
• Muscle biopsy: shows degeneration, loss of fibers, and increased fat and connective tissue.
• EMG (electromyography): shows low amplitude, short duration polyphasic motor unit action potentials.

DMD - Clinical Picture

• Muscle weakness, becomes apparent at ages 3 to 5
• Symmetrical, proximal greater than distal weakness
• Lower extremities and torso more affected than upper extremities
• Shoulder girdle weakness, excessive scapular winging
• Difficulty performing overhead activities, inability to use assistive devices for ambulation
• Steady decline in strength from 6 to 11 years old
• Calf hypertrophy present at age 5 to 6 years
• Pseudohypertrophy: muscle tissue replaced by fat and fibrous tissue, other muscles may look enlarged (gluteus, vastus lateralis, deltoid)

Clinical Presentation

• Possible delayed onset of motor milestones, especially late walking
• Tripping, falling, poor ability to run, unable to keep up with peers
• Toe walking, pseudohypertrophy of calves
• Progressive weakness, lordosis, waddling gait
• Gower's sign (using hands to push up from thighs to stand)

Medical Management

• Pre-Natal Care: Genetic counseling for families with history, possible in utero testing
• Early Diagnosis: CK levels, genetic testing, biopsy
• Nutritional Management: Obesity is a significant problem; bone health issues
• Orthopedic Management: Lengthening of contractures, spinal stabilization for scoliosis
• Cardiopulmonary Management: including pulmonary function testing

Clinical Progression

• Weakness is steadily progressive; proximal muscles tend to be weaker earlier in the illness and progress faster.
• Lumbar lordosis, wide base of support with gait, contracture development, and slow functional activities.

Progression (different age groups)

• Birth to 2 years: late acquisition of milestones, especially walking
• 3-5 years: toe walking, clumsiness, pseudohypertrophy of calves, Gower's sign
• 6-8 years: toe walking, lordosis, difficulty climbing stairs without assistance, waddling gait, rising from the floor without help
• 9-11 years: walks with braces, scoliosis, possible orthopedic surgery, beginning respiratory insufficiency
• 12-14 years: loss of ambulation, increased respiratory difficulties, obesity, contractures, progression of scoliosis, dependant for transfers, needs assist with ADLs
• 15-17 years: Dependant in most ADLs, may need assisted ventilation
• 18+: Totally dependant, assisted ventilation, death comes after a period of declining respiratory function

Scoliosis

• Scoliosis develops as the age of the child with DMD increases.
• Significant curves are generally not noticed until after the age of 11 years.
• Progress as the back muscles become weaker and as the child spends less time standing and more time sitting.
• Over time, becomes fixed.

Respiratory

• Respiratory musculature atrophies
• Coughing becomes ineffective
• Pulmonary infections become more frequent
• Progressive weakness of the muscles of respiration is the major cause of respiratory complications in DMD.

Cardiac

• Deficiency of dystrophin results in cardiomyopathy, arrhythmias, and congestive heart failure
• The posterobasal portion of the left ventricle is affected more than other parts of the heart
• Heart muscle involvement generally occurs later than skeletal muscle involvement.

Cognitive

• High rate of intellectual impairment and emotional disturbance
• Deficit is not progressive and not related to severity of disease
• IQ scores approximately 1 standard deviation below the mean
• Verbal scores affected more than performance scores.

Importance of Treatment

• Proper treatment can prolong quality of life.
• Parental counseling to reduce guilt, hostility, fear, depression, hopelessness, and other common emotions experienced by parents is important.
• An active physical therapy (PT) program prolongs ambulation and more closely approximates normal independence in later childhood.
• Specific treatments available in the future are most apt to benefit those in optimal physical condition.

Medical Treatment

• Corticosteroids (prednisone, and deflazacort) are effective in increasing strength and improving function for 6 months to 2 years.
• Creatine monohydrate may increase creatine levels in muscles , improve maximal exercise performance, and recovery.
• Investigation of myoblast transplants aims to replace the missing dystrophin protein.

Experimental Treatment

• Cell therapy
• Gene therapy
• Mutation specific medication
• Utrophin/Myostatin drug therapies

Orthopedic Treatment Indications

• Spinal fixation when scoliosis progresses rapidly and spinal curve exceeds 30°.
• Pelvic obliquity, skin breakdown, discomfort, decreased sitting tolerance, and difficulty using upper extremities secondary to lack of trunk stability; need for arm rests
• Achilles tendon lengthening, fasciotomies, tibialis posterior transpositions, and percutaneous tenotomies to increase joint range of motion for prolonged ambulation.

Orthopedic Management - Muscle Lengthening

• Surgical intervention is not universally agreed upon and must be individualized.
• Procedures like Tendo-Achilles lengthening, Hamstring lengthening, TFL lengthening sometimes encouraged in younger children (4-7).
• Middle ambulatory phase tendon lengthening may prolong ambulation for 1-3 years but there is no consensus.

Orthopedic Treatment: Scoliosis

• Monitoring and radiographs for scoliosis should begin early; radiographs are necessary when wheelchair dependency begins.
• Annually assess curves of 15-20 and every 6 months for curves over 20.
• TLSO's are not indicated.
• Spinal fixation is encouraged when scoliosis begins to progress rapidly and the spinal curve exceeds 30 degrees.

Pulmonary Treatment

• Nasal positive pressure ventilation at night assists breathing by resting overworked muscles
• This may take time to feel the benefits but results in improved sleep and increased daytime energy and alertness for the patient.
• Children with advanced respiratory failure may need ventilation day and night.

Cardiac Treatment

• Regular cardiac echocardiograms (ECHO) and electrocardiograms (ECG or EKG) monitoring are needed to monitor these conditions.
• Cardiac medications are often necessary to manage arrhythmias.

Physical Therapy Examination

• 3 phases of presentation: early or ambulatory stage, transitional phase during loss of ambulation, and later stage when the individual uses a wheelchair and is dependent for most functional activities

History

• Family, birth, and developmental history
• Review of systems (cardiac, pulmonary, GI, integumentary, musculoskeletal, functional mobility, social history, durable medical equipment)
• Understanding of child and family concerns is critical prior to examination.
• Developmental history

Review of Systems

• Pulmonary, cardiac, GI, integumentary, and musculoskeletal systems
• Referral to specialist if necessary

Tests and Measures

• Functional abilities, stable performance or declining performance, assessing strength, pulmonary function, and functional tasks in combination.
• 6-minute walk test, Brooks grades for UE, Vignos for LE, energy expenditure index
• Brooke scale for upper extremity, and Vignos scale for lower extremity

Tests and Measures (cont'd)

• Muscle strength (MMT must be a routine part of the physical therapy evaluation)
• No correlation between rate of decline and use of wheelchair
• Hand-held myometers (and other quantified systems) are used to evaluate and quantify muscle strength in boys with DMD.
• ROM (Range of Motion): loss of full ankle dorsiflexion, knee extension, and hip extension with resulting contractures. Measurement of these is crucial for goniometric testing.

Primary Physical Therapy Problems

• Weakness, decreased active and passive ROM, loss of ambulation, decreased functional ability, decreased pulmonary function, emotional trauma (family and individual), progressive scoliosis, and pain

Goals for Physical Therapy

• Prevent deformity (splinting, positioning)
• Improve pulmonary function
• Prolong functional capacity (normal age-appropriate activity, avoid maximal resistive strength training and eccentric exercise, submaximal endurance training, orthopedic surgery, standard or power wheelchair use)
• Facilitate support from family and others
• Control pain (addressing issues of pain through education, proper positioning, lifting techniques, medical treatment and use of creatine)

Therapeutic Interventions

• Prevention of contractures (exercise to maintain maximal function)
• Prevention of obesity
• Maintenance of ambulation
• Respiratory care
• Adaptive equipment and bracing
• Transition to wheelchair
• Addressing psychosocial issues

Physical Therapy Intervention

• Home program is essential (stretching, stretching, stretching, weight control)
• Weight control improves mobility and self-esteem
• Better to prevent excessive weight gain in the young, ambulatory child than obese adolescent

Exercise and Neuromuscular Disease

• All patients should be advised not to exercise to the point of exhaustion due to the risk of muscle damage.
• Patients in exercise programs should be aware of the signs of overwork weakness (feeling weaker than stronger 30 minutes after exercise, excessive DOMS 24-48 hours after exercise, severe muscle cramping, heaviness in the extremities, prolonged shortness of breath).
• Strength training can be prescribed but use caution and a common-sense approach in slow-progressing NMD (12 week moderate strengthening program may increase strength without harmful effects).
• Dystrophin deficient muscle is very susceptible to exercise-induced muscle injury. Be cautious.
• Aerobic exercise can help improve cardiovascular performance and muscle efficiency; gentle low impact exercise (walking, swimming, stationary bike, UBE) improves physical function, fighting depression, maintaining body weight, and improving pain tolerance.

Additional Muscular Dystrophies

• Duchenne: onset 1-4 years, x-linked, rapid progression
• Becker: onset 5-10 years, x-linked, slower progression
• Congenital: onset birth, recessive, slow progression, shortened lifespan
• Congenital Myotonic: onset birth, slow progression, significant intellectual impairment
• Facioscapulohumeral: onset 1st decade, slow progression, late loss of ambulation, variable life expectancy

Myotonic Dystrophy (MTD)

• Autosomal dominant disorder (chromosome 19)
• Symptoms first noticed during adolescence; characterized by myotonia (delay in muscle relaxation time), muscle weakness
• Myotonia decreases as weakness progresses
• Complaints of weakness and stiffness
• Many patients also have cognitive impairment, cataracts, diabetes, cardiac arrhythmias

Limb Girdle Muscular Dystrophy

• Group of progressive muscular dystrophies affecting the proximal musculature
• Variable initial presentation, extending from early childhood into adulthood
• Heterogenous underlying pathology
• Gower's sign, waddling gait

Congenital Myopathy

• Group of diseases including nemaline myopathy, central core myopathy, and centronuclear (myotubular) myopathy
• Results from abnormalities of the sarcomeric proteins
• Characterized by weakness and muscle atrophy that typically presents at birth

Congenital Muscular Dystrophy Incidence and Etiology

• Incidence: 4.65 in 100,000 in the Italian population
• Group of inherited disorders
• Autosomal recessive
• Onset at birth or shortly after

Congenital Muscular Dystrophy

• Those with involvement of central nervous system and without central nervous system involvement
• Fukuyama CMD, Walker-Warburg syndrome, and muscle-eye-brain disease all demonstrate muscle, brain, and eye abnormalities

Spinal Muscular Atrophy

• A disorder manifested by loss of anterior horn cells.
• Results in a phenotypic spectrum of disease states that are often divided into three types based on a functional classification system.

Spinal Muscular Atrophy (Different Types)

• SMA type 1 (Werdnig-Hoffman Acute): onset 0-3 months, recessive, severe hypotonia, death within the first year.
• SMA type 2 (Werdnig-Hoffman Chronic): onset 3 months to 4 years, recessive, rapid progression then stabilizes, moderate to severe hypotonia, shortened lifespan.
• SMA type 3 (Juvenile onset): onset 5-10 years, recessive, slow progression, milder impairments.

SMA Type I

• Incurable genetic disease diagnosed usually in the first 18 months of life.
• Loss of ability to move and walk.
• Patients face significant challenges and often need significant support due to the poor prognosis.

Spinal Muscular Atrophy Type I (Werdnig-Hoffman Disease)

• Noted within the first 3 months of life.
• Mother complaints of decreased fetal movement during pregnancy.
• At birth, the child is hypotonic and has difficulty feeding.
• Muscle wasting is significant, and spontaneous movements are infrequent and of small amplitude.
• The child may present with head lag on pull to sit and will drape over the examiner's hand during a Landau test

Spinal Muscular Atrophy Type II

• Affects infants but is more benign than SMA type I
• Presentation later in the first year of life (child not actively pulling to stand)
• Characterized by weakness and wasting of the extremities and trunk musculature
• Fasciculations are common on examination of the tongue
• Fine tremor when attempting to use limbs
• Mini-polymyoclonus
• Some may learn to walk with bracing

Spinal Muscular Atrophy Type III (Kugelberg-Welander Disease)

• Symptoms of progressive weakness, wasting, and fasciculations.
• Age of presentation can vary from toddler years into adulthood; some classify the latter as type IV.
• Proximal muscles are usually involved first.
• May be confused with muscular dystrophies due to age of presentation.

Spinal Muscular Atrophy Type III (Kugelberg-Welander Disease) (cont'd)

• Deep tendon reflexes are decreased, but contractures are unusual, and progressive spinal deformities are uncommon as long as the child remains ambulatory.
• Diagnosis established by clinical picture and diagnostic laboratory studies, including electromyogram and muscle biopsy (showing denervation).
• Genetic testing shows a deletion of the SMN gene on the fifth chromosome.

Prognosis

• Can be aided by a good developmental history
• Symptoms prior to 2 years have poorer prognosis
• Symptoms after 2 years may maintain ambulation until 44 years of age.
• Symptoms prior to 2 may maintain ambulation until 12 years of age

Charcot-Marie-Tooth Disease

• Common inherited neurological disorder (1 in 2,500 in the US)
• Affects peripheral nerves (also known as hereditary motor and sensory neuropathy or peroneal muscular atrophy)
• CMT1A is an autosomal dominant disease resulting from a duplication on chromosome 17 of the gene that produces PMP-22 (peripheral myelin protein-22). Overexpression of this gene causes abnormalities in the structure and function of the myelin sheath.
• Weakness and atrophy in the lower legs begin in adolescence. Hand weakness and sensory loss may occur later.
• A typical feature includes foot and lower leg muscle weakness, foot drop, high-stepped gait, and frequent tripping or falls.
• Foot deformities like cavus or cavo-varus and hammertoes are common due to weakness of small foot muscles.

Charcot-Marie-Tooth Disease (cont'd)

• Diagnosis: standard medical history, family history, neurological examination. Look for muscle weakness in arms, legs, hands, and feet, decreased muscle bulk, reduced tendon reflexes, and sensory loss. (touch, position sense, vibration)
• Nerve conduction studies and electromyography (EMG)

Charcot-Marie-Tooth Disease (cont'd)

• PT & OT involves muscle strength training, muscle and ligament stretching, and moderate aerobic exercise.
• Treatment programs should start early to delay or reduce muscle atrophy. Exercise is most useful before nerve degeneration.
• Use low-impact exercises such as biking or swimming instead of higher-impact activities like walking or jogging.
• Caring for feet is crucial.
• Podiatrist may be involved to maintain toenails, condition toes, and to treat callus formation.
• High toe box shoes and orthotics (if needed) aid in accommodating pes cavus and equally distributing pressure on feet

Charcot-Marie-Tooth Disease (cont'd)

• Many CMT patients need AFOs (ankle-foot orthoses) or other orthopedic devices to aid everyday mobility and prevent injury
• Thumb splints may improve hand weakness and fine motor function.
• Assistive devices should be considered early to prevent muscle strain and weakening
• Orthopedic surgery may reverse foot and joint deformities (tendon transfers or lengthening).